Hot pickling-bath.



' in order to lower its meltin point.

UNITED STATES PATENT OFFICE.

FREDERICK F. EARNHAM, OF MGKEESPOET, PENNSYLVANIA, ASSIGNOR T0 AMERICAN SHEET & TIN PLATE COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF NEW JERSEY.

No Drawing.

Specification of Letters Patent. Application filed September-8, 1911. -Scria1 No. 648,354.

HOT PICKLING-BATH.

PatentedJune 11, 1912.

To all whom it may concern:

Be it known that I, FREDERICK F. FARN- HAM a resident of McKeesport in the county of Allegheny and State of Pennsylvania, haye invented a new and useful Improvement in Hot Pickling-Baths, of which the following is a specification.

- This invention relates to a cleaning or pickling bath and flux for cleaning the surfaces and removing scale and other impurities from iron and steel articles preparatory to coating them with zinc, tin, lead, or other coating substances or alloys.

The object of the inventionis to provide a bath which not only cleans the iron and steel articles, but also serves as a flux to secure a closer adhesion of the coating whlch is. subsequently applied thereto.

The bath ma be composed entirely of lead chlorid bGl,) but preferabl has added thereto a small amount of tin c orid Lead chlorid alone well answers t e purpose but its melting point can be reduced and its fluidity increased and its viscosit reduced by the addition thereto of a sma amount of tin chlorid, or, more strictlyi speaking, of stannous chlorid (SnCl,). T e amount of stannous chlorid can vary an here from zero to 25 per cent. of the who e. The lead chlorid is generally first melted and then the required amount of stannous chlorid thrown in. The articles to be cleaned are merely dipped into the molten mass and allowed to remain therein long enough to raisethe metal articles to the same temperature as the bath. The time for this vanes according to the bulk of the metal article and also with the tem erature of such article before immersion. The lead chlorid possibly acts as an acid to combine as a whole with the scale or Fe,0, and forms a magneticscum on to of the bath. Possibly a lead-iron orid is formed.

A thin coating of lead may be formed on the iron-or stee article in the bath, or the surface simply cleaned leaving the bright 11011 covered with the constituents of the bath as a protection against oxidation when taken out and exposed to the air. This protective covering acts as a flux in the coating pot. The scum which is removed can be treated 'to recover the lead chlorid, so that there is no waste. 4

The bath is volatile at a high temperature but is not volatile at the tem erature at which it is used if a draft of air is not permitted to blow over it, hence the loss by volatization can be made small by a suitcan be readily recovered, and used over again. It thoroughly cleans the surface of the iron or steel articles from all scale and other im urities and leaves the same coated with a 'n flux coatin which greatly increases the adhesion of t e coating substance ap lied to the article.

at I claim is:

1. A clean molten lead orid.

2. A cleaning and fluxing bath consisting of molten lead chlorid and stannous chlori 3. A cleaning and fluxing bath consistin of molten lead chlorid and stannous chlori the latter not exceeding 25 per cent. of the whole.

In testimony whereof I have hereunto set my hand.

FRED. F. FARNHAM.

Witnesses:

F. W. Home, Mar E. Gmoon.

and fluxing bath containing 

